The fuel contained within the fuel-tank and fuel lines of an automotive vehicle may evaporate, releasing volatile organic compounds in the form of hydrocarbon vapor. That vapor may escape to the atmosphere, causing pollution in the form of evaporative emissions. Due to stringent air quality standards in the United States and other countries, automobile manufacturers constantly work to decrease evaporative emissions through the modern automobiles manufactured and introduced in the market.
Most modern vehicles incorporate an Evaporative Emission control system (EVAP) configured to reduce or minimize evaporative emissions. An EVAP system principally works by trapping and storing hydrocarbon vapors emerging from the fuel-tank, in a canister containing adsorbent carbon (carbon canister), and eventually, reintroducing the stored vapors to the engine, for combustion. Specifically, a fluid flow line links the fuel tank and the carbon canister, allowing vapor to flow to the canister from the tank. A second fluid flow line links the canister and the engine. A canister purge valve (CPV) is positioned in the second fluid line, and that valve is normally closed. The vehicle's Powertrain Control Module (PCM) opens the CPV at specific times, when the engine is running. As the CPV is opened, fresh air is drawn from the canister to the engine, entraining vapors stored within the canister and introducing them into the engine for combustion. That process is known as ‘purging’ the canister.
Any leakage within an EVAP emission system of a vehicle may contribute significantly to pollution. Therefore, the EVAP system should be completely leakage free. Regulations introduced by the Onboard Diagnostic system Generation II (OBD II) require that the EVAP systems should be checked for leaks as small as 0.02 inches in diameter.
Some OEMs do not commence the EVAP leak detection process until sufficient fuel cooling has occurred to create a natural vacuum within the system. Such cooling can require several hours, and thus some methods of leak detection require waking up the PCM arbitrarily, hours after the engine shutoff. Running tests at such times can require excess battery and system cycling, as well as incurring operator issues. For hybrid electric vehicles (HEV's), wasting battery power has a significant impact, as reductions in battery charge levels translate directly to reduced range on electric power. That effect requires additional operation of the combustion engine, which in turn directly impacts overall fuel economy. Thus, a small event can have serious consequences.
Considering the problems mentioned above, and other shortcomings in the art, there exists a need for an appropriate system and a method for performing leakage detection within the EVAP system of an automotive vehicle, which can activate the PCM at an appropriate time for detecting leakage.